Hey guys. I had the same problem. The way I fixed it is to unregister the software on my Mac, then add a protected eBook. It asked me to enter my authorisation credentials, which I did and the eBook added itself smoothly.

I haven't tried adding a second book yet, but at least I got the first one on.

I am having the same problem. On my new PC (Windows 8) it does not work with E_ACT_NOT_READY. At he very same time on my old PC (Win 7) I can open the document. Since I have to return the old PC to the company I work for, this is a serious problem for me.

I have a brand new Macbook Air, running Yosemite. I had this problem and did what was suggested - deleted the .dat file and reauthorized. The book I want is now showing up in ADE without error messages, but every time I try to transfer it to my Kobo, ADE crashes. Worked perfectly on my old PC; very frustrated.

I have a mac mini running 10.10.2 ADE 3.0.86137. I use a NOOK, but I would be so surprised if the ereader difference was a factor. The downloaded epub (acsm) files transfer to the nook without issue in my case. Best of luck.

After being unable to download books bought on Google Play via acsm, getting the E_ACT_NOT_READY error, I did as others have suggested and deleted the (hidden as derekdokoto mentions). I then tried opening one of my Play acsm purchases and got this authorization screen:

Previously I had used the default Adobe authorization, not realizing that you can put in credentials for the specific book vendor.

Rather than go through the trouble of entering my various logins, I chose to continue without authorizing, because I wanted just a couple of specific books to read while traveling:

As an aside, my multiple attempts to download the books from Play resulted in their servers thinking I had reached the limit for the number of devices to which I could download, even though all the installations failed! I had to get Google Play support to reset my device limit, then all was well.

In my case the workaround of "Navigate to /Users/Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash" then relaunching the .ascm file allowed reauthorization.

The bug, in my case, is that Adobe didn't handle the use case of restoring from backup. Since authorization is device specific, I couldn't deauthorize because I wasn't using the original device. Deleting activation.dat allowed authorization as a new machine.

Adobe needs to add device deauthorization to the Adobe ID profile -- Google and Apple do this for the devices they track. They also need to fix the code so it handles the cause of a machine-specific authorization file on a new machine -- it should ask user if the old machine should be deauthorize, then request new machine specific authorization and it should "explain" why the authorization is needed.

I tried to erase authorization many times. That ist not possible. Message from ADE: "Unable to Erase Authorization. Please try after some time".

Then I erased the authorization localy and authorized again. At this time there is no Error Message. The authorization seems to be successfull, but when I try to open a book I got the Error E_ACT_NOT_READY.

In my case the workaround of "Navigate to /Users/Library/Application Support/Adobe/Digital Editions and drag the activation.dat file to the trash" then relaunching the .ascm file allowed reauthorization.

The bug, in my case, is that Adobe didn't handle the use case of restoring from backup. Since authorization is device specific, I couldn't deauthorize because I wasn't using the original device. Deleting activation.dat allowed authorization as a new machine."@